PR: Migrate TalentPlus to USDC-Only Payments

Overview

This PR migrates the TalentPlus subscription system from ETH payments to USDC (ERC20) payments only. The changes ensure a more stable payment mechanism using a stablecoin while maintaining all existing functionality including TALENT-based discounts and subscription management features.

Changes Summary

🔄 Contract Changes

1. TalentPlus.sol

• ✅ Removed: ETH payment support (payable modifier and msg.value handling)
• ✅ Added: USDC payment token support via constructor parameter
• ✅ Updated: subscribe() function now accepts tokenAmount parameter instead of ETH
• ✅ Added: SafeERC20 integration for secure token transfers
• ✅ Updated: Event signature changed from finalPrice to pricePaid

Key Changes:

• Constructor now requires paymentToken address (USDC: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base)
• Users must approve the contract to spend USDC before subscribing
• Automatic refund of excess tokens (similar to ETH refunds)

2. TalentPlusSubscription.sol

• ✅ Renamed: priceInEth → price throughout the contract
• ✅ Updated: All price references now indicate USDC (6 decimals)
• ✅ Updated: Function parameters and return values use price instead of priceInEth
• ✅ Updated: Events emit price instead of priceInEth
• ✅ Updated: Documentation comments reference USDC instead of ETH

Key Changes:

• addSubscriptionModel(): priceInEth parameter → price parameter
• updateSubscriptionModel(): priceInEth parameter → price parameter
• getSubscriptionModel(): Returns price instead of priceInEth
• calculateDiscountedPrice(): Uses model.price instead of model.priceInEth

🧪 Test Updates

1. TalentPlusSubscription.ts

• ✅ Updated test assertions: model.priceInEth → model.price (2 occurrences)

2. TalentPlus.ts

• ✅ Added payment token (USDC mock) deployment in beforeEach
• ✅ Updated constructor calls to include paymentToken parameter
• ✅ Replaced all ETH payments ({ value: ... }) with token payments
• ✅ Updated all subscribe() calls to use tokenAmount parameter
• ✅ Added token minting and approval setup for test users
• ✅ Updated event assertions: finalPrice → pricePaid
• ✅ Updated error message expectations: "Insufficient ETH payment" → "Insufficient token payment"

📜 Script Updates

1. deployTalentPlus.ts

• ✅ Added USDC address constant: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
• ✅ Updated deployTalentPlus() call to include USDC address
• ✅ Updated verification command to include payment token parameter

2. shared/index.ts

• ✅ Updated deployTalentPlus() function signature to accept paymentToken parameter

Breaking Changes

⚠️ Contract Interface Changes

1. TalentPlus Constructor

   // Before
   constructor(address _talentPlusSubscriptionAddress, address _feeReceiver)
   
   // After
   constructor(address _talentPlusSubscriptionAddress, address _feeReceiver, address _paymentToken)

2. TalentPlus.subscribe()

   // Before
   function subscribe(address wallet, string memory subscriptionSlug) public payable
   
   // After
   function subscribe(address wallet, string memory subscriptionSlug, uint256 tokenAmount) public

3. TalentPlusSubscription Functions

   // Before
   function addSubscriptionModel(..., uint256 priceInEth, ...)
   function getSubscriptionModel(...) returns (..., uint256 priceInEth, ...)
   
   // After
   function addSubscriptionModel(..., uint256 price, ...)
   function getSubscriptionModel(...) returns (..., uint256 price, ...)

⚠️ Event Changes

TalentPlus.SubscriptionCreated

// Before
event SubscriptionCreated(..., uint256 finalPrice, bool discountApplied);

// After
event SubscriptionCreated(..., uint256 pricePaid, bool discountApplied);

Migration Guide

For Users

1. Approve USDC Spending

   // Users must approve TalentPlus contract to spend USDC
   usdc.approve(talentPlusAddress, amount);

2. Subscribe with USDC

   // Before (ETH)
   talentPlus.subscribe(wallet, "premium", { value: parseEther("100") });
   
   // After (USDC)
   talentPlus.subscribe(wallet, "premium", parseUnits("100", 6)); // 100 USDC

Testing

All tests have been updated and are passing:

✅ 60 tests passing
  - TalentPlus: 20 tests
  - TalentPlusSubscription: 40 tests

Run tests with:

npm test -- --grep "TalentPlus"

Security Considerations

• ✅ SafeERC20: Uses OpenZeppelin's SafeERC20 for secure token transfers
• ✅ Reentrancy Protection: Maintains nonReentrant modifier
• ✅ Input Validation: All parameters validated (zero addresses, empty strings, etc.)
• ✅ Automatic Refunds: Excess tokens automatically refunded to users
• ✅ No Exchange Rate Risk: Direct USDC pricing eliminates ETH/USD volatility

Benefits

1. Price Stability: USDC provides stable pricing without ETH volatility
2. Better UX: Users can pay with stablecoins instead of volatile ETH
3. Simpler Pricing: Direct USDC prices eliminate exchange rate complexity
4. Maintained Features: All existing features (discounts, extensions, etc.) work identically

Deployment Checklist

• Deploy updated TalentPlusSubscription contract
• Deploy updated TalentPlus contract with USDC address
• Add TalentPlus as trusted signer in TalentPlusSubscription
• Set up subscription models with USDC prices
• Update frontend to use USDC payments
• Test subscription flow end-to-end
• Update documentation

Files Changed

Contracts

• contracts/talent_plus/TalentPlus.sol
• contracts/talent_plus/TalentPlusSubscription.sol

Tests

• test/contracts/talent_plus/TalentPlus.ts
• test/contracts/talent_plus/TalentPlusSubscription.ts

Scripts

• scripts/talent_plus/deployTalentPlus.ts
• scripts/shared/index.ts

Related Issues

• Migrates payment system from ETH to USDC
• Improves price stability for subscription payments
• Maintains backward compatibility for subscription logic

Notes

• USDC address on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
• Prices are in USDC units (6 decimals)
• All discount logic remains unchanged
• Subscription extension/upgrade logic unchanged